/* dualview.c -- 位字段和按位运算符 */
#include <stdio.h>
#include <stdbool.h>
#include <limits.h>

/* 位字段符号常量 */
/* 边框线样式  */
#define SOLID 0
#define DOTTED 1
#define DASHED 2

/* 三原色 */
#define BLUE 4
#define GREEN 2
#define RED 1

/* 混合颜色 */
#define BLACK 0
#define YELLOW (RED | GREEN)
#define MAGENTA (RED | BLUE)
#define CYAN (GREEN | BLUE)
#define WHITE (RED | GREEN | BLUE)

/* 按位方法中用到的符号常量 */
#define OPAQUE 0x1
#define FILL_BLUE 0x8
#define FILL_GREEN 0x4
#define FILL_RED 0x2
#define FILL_MASK 0xE
#define BORDER 0x100
#define BORDER_BLUE 0x800
#define BORDER_GREEN 0x400
#define BORDER_RED 0x200
#define BORDER_MASK 0xE00
#define B_SOLID 0
#define B_DOTTED 0x1000
#define B_DASHED 0x2000
#define STYLE_MASK 0x3000

const char *colors[8] = {"black", "red", "green", "yellow", "blue", "magenta", "cyan", "white"};

struct box_props
{
    bool opaque : 1;
    unsigned int fill_color : 3;
    unsigned int : 4;
    bool show_border : 1;
    unsigned int border_color : 3;
    unsigned int border_style : 2;
    unsigned int : 2;
};

union Views /* 把数据看作结构或unsigned short类型的变量 */
{
    struct box_props st_view;
    unsigned short us_view;
};

void show_settings(const struct box_props *pb);
void show_settings1(unsigned short);
char *itobs(int n, char *ps);

int main(void)
{
    /* 创建Views联合，并初始化initialize struct box view */
    union Views box = {{true, YELLOW, true, GREEN, DASHED}};
    char bin_str[8 * sizeof(unsigned int) + 1];
    printf("Original box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);
    printf("bits are %s\n", itobs(box.us_view, bin_str));

    box.us_view &= ~FILL_MASK;               /* 把表示填充色的位清0 */
    box.us_view |= (FILL_BLUE | FILL_GREEN); /* 重置填充色 */
    box.us_view ^= OPAQUE;                   /* 切换是否透明的位 */
    box.us_view |= BORDER_RED;               /* 错误的方法 */
    box.us_view &= ~STYLE_MASK;              /* 把样式的位清0 */
    box.us_view |= B_DOTTED;                 /* 把样式设置为点 */
    printf("\nModified box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);
    printf("bits are %s\n", itobs(box.us_view, bin_str));
    return 0;
}

void show_settings(const struct box_props *pb)
{
    printf("Box is %s.\n", pb->opaque == true ? "opaque" : "transparent");
    printf("The fill color is %s.\n", colors[pb->fill_color]);
    printf("Border %s.\n", pb->show_border == true ? "shown" : "not shown");
    printf("The border color is %s.\n", colors[pb->border_color]);
    printf("The border style is ");
    switch (pb->border_style)
    {
    case SOLID:
        printf("solid.\n");
        break;
    case DOTTED:
        printf("dotted.\n");
        break;
    case DASHED:
        printf("dashed.\n");
        break;
    default:
        printf("unknown type.\n");
    }
}
void show_settings1(unsigned short us)
{
    printf("box is %s.\n", (us & OPAQUE) == OPAQUE ? "opaque" : "transparent");
    printf("The fill color is %s.\n", colors[(us >> 1) & 07]);
    printf("Border %s.\n",
           (us & BORDER) == BORDER ? "shown" : "not shown");
    printf("The border style is ");
    switch (us & STYLE_MASK)
    {
    case B_SOLID:
        printf("solid.\n");
        break;
    case B_DOTTED:
        printf("dotted.\n");
        break;
    case B_DASHED:
        printf("dashed.\n");
        break;
    default:
        printf("unknown type.\n");
    }
    printf("The border color is %s.\n",
           colors[(us >> 9) & 07]);
}

char *itobs(int n, char *ps)
{
    int i;
    const static int size = CHAR_BIT * sizeof(int);
    for (i = size - 1; i >= 0; i--, n >>= 1)
        ps[i] = (01 & n) + '0';
    ps[size] = '\0';
    return ps;
}